1. Field of the Invention
The present invention relates to position detecting system and method, and more specifically to position detecting system and method for detecting the position and the size of a portion to be measured in a sample, such as a wiring pattern and a contact hole in a semiconductor wafer.
2. Description of Related Art
In the prior art, it is known that a secondary electron image of the scanning electron microscope (abbreviated to “SEM”) is used in order to detect the size of a portion to be measured in a sample, such as a wiring pattern in a semiconductor wafer. For example, in the case of measuring the line width of the wiring pattern on the semiconductor wafer, an electron beam is irradiated perpendicularly to a surface of the semiconductor wafer and is scanned at a constant speed to cross the wiring pattern. The secondary electrons generated in the above process are detected, and the change of the intensity of the secondary electrons is obtained as a function of the scanning position. Since the intensity of the detected secondary electrons changes at the position of the wiring pattern, the size of the wiring pattern in a measured region can be calculated from the change of the intensity of the detected secondary electrons.
However, when a conducting wiring pattern is scanned with the electron beam, the precision of the detection often lowers because the wiring pattern is electrified or charged. A method for overcoming this problem has been proposed in Japanese Patent Application Pre-examination Publication No. JP-A-01-197607, (the content of which is incorporated by reference in its entirety into this application, and also an English abstract of JP-A-01-197607 is available from the Japanese Patent Office and the content of the English abstract of JP-A-01-197607 is also incorporated by reference in its entirety into this application).
Now, the method proposed by JP-A-01-197607 will be briefly described with reference to FIG. 7, which is a sectional view of a circuit component as a sample to be measured.
The shown circuit component, generally designated with Reference Numeral 100, includes a conducting substrate 101. An insulating film 102 is deposited on a surface of the conducting substrate 101, and a contact hole 103 is formed to penetrate through the insulator film 102. A conducting film 104 is deposited on a surface of the insulating film 102 to contact with the surface of the conducting substrate 101 through the contact hole 103.
In the circuit component 100 thus formed, since the conducting film 104 is electrically connected to the conducting substrate 101 through the contact hole 103 formed in the insulating film 102, even if the surface of the conducting film 104 is scanned with the electron beam in the scanning electron microscope (SEM), the conducting film 104 is in no way electrified. Therefore, the size of the conducting film 104 can be precisely determined from the intensity of the secondary electrons. As mentioned above, since a structure for preventing electrification of the conducting film 104 is realized by the contact hole 103 formed in the insulating film 102, the structure is simple and does not require special equipment for formation of the structure.
Incidentally, when it is required to measure the diameter of the contact hole 103 in the circuit component 100, it is sufficient if, before the conducting film 104 is deposited, the surface of the insulating film 102 is scanned with the electron beam in the scanning electron microscope (SEM) and the generated secondary electrons are detected.
The circuit component 100 formed as mentioned above can make it possible to precisely measure the line width of the conducting film 104 by scanning the electron beam, and also to measure the diameter of the contact hole 103 by the scanning of the electron beam in the process of manufacturing.
However, even if it is easy to detect the position and the diameter of the upper end of the contact hole 103 by the scanning of the electron beam, it is difficult to detect the position and the diameter of the bottom of the hole. The reason for this is that, when the contact hole 103 is deep, even if the electron beam is irradiated, the secondary electrons are not emitted out of the contact hole.